Adsorption of Er(Ⅲ ) and Its Mechanism on Diglycolamidic Acid Resin

The adsorption behavior and mechanism of a novel chelate resin, diglycolamidic acid resin (DAAR) for Er(Ⅲ) were investigated. The optima adsorption condition of DAAR for Er(Ⅲ) is pH 6.20 in HAc NaAc medium. The statically saturated adsorption capacity is 189 mg·g -1 resin at 298 K. The Er (Ⅲ) adsorbed on DAAR can be eluted reaching 100% by 2 mol·L -1 HCl used as eluant. The resin can be regenerated and reused without apparent decreasing of adsorption capacity. The apparent adsorption rate constant is k 298 =1.94×10 -5 s -1 . The apparent activation energy is 24.7 kJ·mol -1 . The adsorption behavior of DAAR for Er(Ⅲ) obeys the Freundlich isotherm. The thermodynamic adsorption parameters, enthalpy change Δ H of DAAR for Er(Ⅲ) is 24.1 kJ·mol -1 . The molar coordination ratio of the functional group of DAAR to Er (Ⅲ) is 3∶1. The adsorption mechanism of DAAR for Er (Ⅲ) was examined by using chemical method and IR spectrometry. The coordination compound is formed between oxygen atoms in the functional group of DAAR and Er(Ⅲ).

A review of cadmium sorption mechanisms on soil mineral surfaces revealed from synchrotron-based X-ray absorption fine structure spectroscopy:Implications for soil remediation

The sorption of cadmium(Cd) is one of the most important chemical processes in soil, affecting its fate and mobility in both soil and water and ultimately controlling its bioavailability. In order to fundamentally understand the sorption/desorption of Cd in soil systems, X-ray absorption fine structure spectroscopy(XAFS) has been applied in numerous studies to provide molecular-level information that can be used to characterize the surface adsorption and precipitation reactions that Cd can undergo. This information greatly improves our current knowledge of the possible chemical reactions of Cd in soil. This paper critically reviews the mechanisms of Cd sorption/desorption at the mineral-water interface based on XAFS studies performed over the past twenty years. An introduction to the basic concepts of sorption processes is provided, followed by a detailed interpretation of XAFS theory and experimental data collection and processing,ending finally with a discussion of the atomic/molecular-scale Cd sorption mechanisms that occur at the soil mineral-water interface. Particular emphasis is placed on literature that discusses Cd adsorption and speciation when associated with iron, manganese, and aluminum oxides and aluminosilicate minerals.Multiple sorption mechanisms by which Cd is sorbed by these minerals have been found, spanning from outer-sphere to inner-sphere to surface precipitation,depending on mineral type, surface loading, and pH. In addition, the application of complementary techniques(e.g.,113 Cd nuclear magnetic resonance(NMR) and molecular dynamics simulation) for probing Cd sorption mechanisms is discussed. This review can help to develop appropriate strategies for the environmental remediation of Cd-contaminated soils.

Mechanism for Cu^(2+) Sorption on Palygorskite

A single-factor experiment of copper ion adsorption on pure palygorskite was carried out to understand the Cu2+ sorption of palygorskite—an important clay mineral in soil and sedimentary rock. In addition, pH of the solution and the surface microstructure of palygorskite were investigated before and after adsorption. The experimental results indicated that efficiency of Cu2+ removal was related to the oscillation rate of the specimen shaker, sorption time, initial pH value and the amount of adsorbent added. Palygorskite induced Cu2+ hydrolysis and interaction between copper hydroxide colloids and palygorskite surfaces, as observed with transmission electron microscopy (TEM), were the main contributions to palygorskite removal of Cu2+. This mechanism was different from adsorption at the mineral-water interface. It was proposed that surface hydrolysis of palygorskite raised the alkalinity of the palygorskite-water interface and suspension system. Thus, the induced pH of the solution was then high enough for Cu2+ hydrolysis on the mineral surface and in solution.

Sorption Behavior and Mechanism of Indium(Ⅲ) onto Amino Methylene Phosphonic Acid Resin

The sorption behavior of amino methylene phosphonic acid resin (APAR) for In (Ⅲ ) was investigated . Experimental results show that In ( Ⅲ ) adsorbed on APAR can be elated with 2mol · L -1 HCl. The apparent rate constant is k29 = 1.50 × 10-5s-1. The sorption behavior of APAR for In ( Ⅲ ) obeys the Freundlich isotherm. The themodynamic parameters of sorption, enthalpy change ()H, free energy change ()G and entropy change ()S of sorption (APAR) for In ( Ⅲ ) are 24.1 kJ·mol-1, -35. 1kJ· mol-1 and 200J· mol-1·K-1 respectively. The coordination molar ratio of the functional group of APAR to In( Ⅲ ) is 2:1. The sorption mechanism of APAR for In( Ⅲ ) was examined by IR spectrometry.

Sorption Behavior and Mechanism of D113 Resin for Erbium

The sorption behavior and mechanism of a novel macroporous weak acid resin(D113 resin) for Er(Ⅲ) were investigated. The optimal sorption condition of D113 resin for Er(Ⅲ) was pH 6.42 in HAc-NaAc medium. The statically saturated sorption capacity was 272 mg·g-1 at 298 K in HAc-NaAc medium. The Er(Ⅲ) adsorbed on D113 resin could be reductively eluted by the mixed solution of HCl and NaCl. The elution percentage could reach 100%. The resin could be regenerated and reused without apparent decrease of sorption capacity. The apparent sorption rate constant was k298=1.98×10-5 s-1. The apparent activation energy was 8.60 kJ·mol-1. The sorption behavior of D113 resin for Er(Ⅲ) obeyed the Freundlich isotherm and Langmuir isotherm. The sorption parameters of thermodynamics were ΔH=44.0 kJ·mol-1, ΔS=223 J·mol-1·K-1, ΔG298 K=-22.3 kJ·mol-1, respectively. The molar coordination ratio of the functional group of D113 resin to Er(Ⅲ) was 3∶1. The sorption mechanism of D113 resin for Er(Ⅲ) was examined using chemical method and IR spectrometry.

Investigation of chlorinated phenols sorption mechanisms on different layers of the Danube alluvial sediment

The characteristics of the Danube river alluvial sediment are of great importance in assessing the risk for transport of pollutants to drinking water sources. Characterization of the sediment column layers has shown that the alluvial sediment, sampled near the city of Novi Sad, is a mesoporous sandy material with certain differences in the properties of individual layers. In order to investigate the sorption mechanisms of four chlorinated phenols(CPs) on the alluvial deposit, static sorption experiments were performed at pH 4, 7 and 10. The results of sorption experiments, confirmed by principal components analysis sugest different mechanisms govern the sorption process at different p H conditions. This can be attributed to the molecular characteristics of CPs, geosorbent properties and to variations in the surface charge of the sorbent at different p H conditions.

SORPTION OF PHENOL AND P-NITROPHENOL ONTO A WEAKLY ANION EXCHANGER: XPS ANALYSIS AND MECHANISM

X-ray photoelectron spectroscopy(XPS)was adopted to elucidate sorption mechanism of phenol and p-nitrophenol onto a weakly anion exchanger D301.The distribution of specific forms of tertiary amino group on D301 was obtained and effect of free tertiary amino group on phenol sorption onto D301 was discussed. The result indicated that the percent of the protonated tertiary amine group on polymeric matrix was much lower than the reference compound N,N-dimethylbenzylamine at an identical pH value in solution due to the much lower activity degree of hydrogen ion in inner resin phase than in the external solution. Less free amino group on D301 results in less sorption capacity of phenol and p-nitrophenol in an acidic solution. Under the experimental conditions both phenol sorption onto D301 can be explained as solid extraction and the distribution coefficient varies linearly with the content of free amino group on D301.

ADSORPTION OF SAMARIUM(III) ON DIGLYCOLAMIDIC ACID RESIN

The sorption behavior and mechanism of a novel chelate resin, diglycolamidic acid resin (DAAR), for Sm(III) were investigated. The optimal sorption condition of DAAR for Sm(III) is pH=6.0 in HAc-NaAc medium. The statically saturated sorption capacity is 190mg/g resin at 298K. The Sm(III) adsorbed on DAAR can be eluted reaching 100% by 0.5~2.0mol/L HCl used as eluant. The resin can be regenerated and reused without apparent decrease of sorption capacity. The apparent sorption rate constant is k298= 1.96×10-5s-1. The apparent activation energy is 26kJ/mol. The sorption behavior of DAAR for Sm(III) obeys the Freundlich isotherm. The thermodynamic sorption parameters, enthalpy change 腍 of DAAR for Sm(III) is 16.9kJ/mol. The molar coordination ratio of the functional group of DAAR to Sm (III) is 3. The sorption mechanism of DAAR for Sm(III) was examined by using chemical method and IR spectrometry. The coordination bond was formed between oxygen atoms in the functional group of DAAR and Sm(III).

Sorption of Organic Compounds in Soil Organic Matter

Soil organic matter(SOM)is the predominant component for sorption of hydrophobic organic compouds in soil and sorption by SOM ultimately affects chemical fate and availability in soil,and the degree of remedia- tion success of contaminated soils. This paper summarizes the latest development on sorption of organic com- pounds in soil (natural) organic matter,addresses four sorption mechanisms: surface adsorption,solid - phase Partitioning,dual-mode sorption,and fixed-pore sorption model,and presents future research directions as well.

Kinetics and Thermodynamic Studies: Adsorption of Pb, Cr and Ni Ions from Spent Lubrication Oil (SLO) Using Acid Modified Clay

Adsorption of Pb, Cr, and Ni ions from spent lubrication oil (SLO) by sulphuric acid modified clay (SAMC) was investigated considering the effect of contact time and temperature of the adsorption system. The removal percentage of the heavy metals was found to be temperature and contact time-dependent. Adsorption of the heavy metals increases with an increase in temperature and contact time with 95.0% - 100% adsorption recorded at the temperature of 331 K with the equilibration time of 12 hours. The thermodynamic and kinetics investigation of the adsorption process showed that the adsorption of these metals by the modified adsorbent is a spontaneous and endothermic physical adsorption process that followed the pseudo-second-order kinetic model.

Diphenylarsinic acid sorption batch experiments and mechanisms in soils using EXAFS spectroscopy

Diphenylarsinic acid(DPAA)is a phenyl arsenic compound derived from chemical warfare weapons.Macroscopic and microscopic work on DPAA sorption will provide useful information in predicting the partitioning and mobility of DPAA in the soil-water environment.Here,batch experiments and extended X-ray absorption fine structure(EXAFS)spectroscopy were used to investigate the sorption mechanisms of DPAA.The DPAA sorption data from 11 soil types was found to fit the Freundlich equation,and the sorption capacity,Kf,was significantly and positively correlated with oxalateextractable Fe2o3.The Kf values of eight of the 11 untreated soils(1.51113.04)significantly decreased upon removal of amorphous metal(hydr)oxides(0.51-13.37).When both amorphous and crystalline metal(hydr)oxides were removed from the untreated soils,the values either decreased or slightly increased(0.65-3.09).Subsequent removal of soil organic matter from these amorphous and crystalline metal(hydr)oxide-depleted samples led to ftirther decreases in A^f to 0.021.38,with only one exception(Sulfic Aquic-Orthic Halosols).These findings strongly suggest that ligand exchange reactions with amorphous metal(hydr)oxides contribute most to DPAA sorption on soils.EXAFS data provide further evidence that DPAA primarily formed bidentate binuclear(~C)and monodentate mononuclear(1 V)coring-sharing complexes with As-Fe distances of 3.34 and 3.66 A,respectively,on Fe(hydr)oxides.Comparison of these results with earlier studies suggests that 2C and 1 F complexes of DPAA may be favored under low and high surface coverages,respectively,with the formation of 1 V bonds possibly conserving the sorption sites or decreasing the steric hindrance derived from phenyl substituents.

Preparation and Properties of A Novel Adsorbent for Selective Removal of Anions from Aqueous Solution

Zeolite modified by lanthanum compounds would be an excellent wnter purification agent that can simultaneously remove both cations and anions in aqtwous solution. For this purpose, a novel adsorbent was prepared by loading lanthanide on the zeolite, and the optimum manufacturing conditions were achieved. The concentration of the modifying solution was 0.5M, in which zeolites .should be kept for 2 hours. The applicable solid/ liquor ratio was 1：25 nt pH10, and the sample was sintered at 600 ℃ for an hour. In addition, the adsorption capacity of modified zeolite for removing different anions from aqueous solution and its regeneration were ulso investigated. The results indicate that high performances uf the novel adsorbent make it possible to be manufactured in industy .

Sorption of lanthanide ions on biochar composites

Sorption of lanthanum（Ⅲ）, cerium（Ⅲ and neodymium（Ⅲ） ions from the aqueous solutions of mixtures through adsorption on the biochar composites was investigated as a function of sorbent mass, pH, phase contact time and initial concentration of solutions at 295 K. The maximum removal of lanthanide ions takes place under the following conditions： 0.1 g of sorbent mass, pH 4 and 360 rain contact time for all studied initial concentrations of solutions. Kinetics of La（Ⅲ）, Ce（Ⅲ） and Nd（Ⅲ） ions sorption proceeded by a fast initial uptake reached equilibrium. This process was modelled by means of the pseudo first order, pseudo second order, intraparticle diffusion and Elovich models. The desorption of three lanthahide ions by nitric, hydrochloric and sulfuric acids at a concentration of 1 mol/L from biochar composites was also studied. In order to investigate the sorption mechanism FFIR, XRD and XPS analyses were performed after sorption of ions from the mixture.

Physicochemical disintegration of biochar:a potentially important process for long-term cadmium and lead sorption

Cadmium(Cd)and lead(Pb)contaminated soils that are used for food production can lead to metal bioaccumulation in the food chain and eventually affect human health.In these agroecosystems,means by which Cd and Pb bioavailability can be reduced are desperately required,with biochar as a proxy for bioavailability reductions.Molecular Cd and Pb sorption mecha-nisms within short-(0-2 years)or long-term(8-10 years)time periods following biochar application to a contaminated rice paddy soil were investigated.A combination of Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy,and soft X-ray imaging was utilized to discern potential metal sorption mechanisms.Following both short-and long-term biochar applications,soil Cd and Pb bioavailable fractions shifted partially towards metal(hydr)oxide and carbonate pre-cipitates,and partially towards biochar-organic function group associations;oxygen-containing groups,such as C=O and O-H,appeared to bind Cd and Pb.Soft X-ray imaging results suggested that heavy metals were primarily sorbed on biochar exterior surfaces,yet given time and particle disintegration,metals sorbed onto biochar interior pore walls.Findings sug-gest that biochar may play a pivotal role in reducing long-term bioavailable Cd and Pb in contaminated soils.Observations also support previous findings that suggest biochar use can lead to reduced heavy metal transfer to plants and potentially to reduced heavy metal consumption by humans.

Removal of fluoride from water using titanium-based adsorbents

Three adsorbents including TiO_(2),Ti-Ce,and Ti-La hybrid oxides were prepared to remove fluoride from aqueous solution.The Ti-Ce and Ti-La hybrid adsorbents obtained by the hydrolysis-precipitation method had much higher sorption capacity for fluoride than the TiO_(2) adsorbent prepared through hydrolysis.Rare earth(Ce and La)oxides and TiO_(2) exhibited a synergistic effect in the hybrid adsorbents for fluoride sorption.The sorption equilibrium of fluoride on the three adsorbents was achieved within 4 h,and the pseudo-second-order model described the sorption kinetics well.The sorption isotherms fitted the Langmuir model well,and the adsorption capacities of fluoride on the Ti-Ce and Ti-La adsorbents were about 9.6 and 15.1 mg·g^(-1),respectively,at the equilibrium fluoride concentration of 1.0 mg·L^(-1),much higher than the 1.7 mg·g^(-1) on the TiO_(2).The sorption capacities of fluoride on the three adsorbents decreased significantly when the solution pH increased from 3 to 9.5.The electrostatic interaction played an important role in fluoride removal by the three adsorbents,and Fourier transform infrared(FTIR)analysis indicated that the hydroxyl groups on the adsorbent surface were involved in fluoride adsorption.